This is an improvement relating to the subject matter of U.S. Pat. Nos. 4,095,757, and 4,165,056 the disclosures of which are incorporated herein and made a part hereof by reference. These patents illustrate the use of plural longitudinally spaced stacks of rotatable elements which are contained within a housing opening upon a yarn passageway or channel contained within a hardened yarn channel forming member which is illustrated as a ceramic member. These constructions do not make adequate provision for threading of the yarn into the yarn channel because in the first of the patents the yarn channel is not sufficient to retain the yarn or prevent longitudinal dislocation of the rotatable elements. The other of the patents illustrates an apparatus which must be threaded longitudinally raising each of the rotatable elements which occasions considerable difficulty during threading.
Accordingly, it is an important object of this invention to provide a yarn tension device employing stacks of cylindrical rollers which may be threaded in a single motion through a lateral opening or passageway opening beneath the rollers for facilitating threading while at the same time maintaining the yarn in threaded position beneath the rollers during tensioning.
Another object of the invention is to maintain the roller members especially when there is only one roller in a stack against longitudinal dislocation while maintaining the roller in position against lateral dislocation.
Another object of the invention is to provide a means for readily parting the thread should the yarn path be dislocated because of excessive tensioning while positioning the yarn path so as to make possible raising and lowering respective stacks of rollers for compensating against unusual tension being placed in the yarn.
Another object of the invention is to provide a central raised portion beneath each of the stacks of rollers in a central longitudinal plane so as to present the yarn for engagement by the lowermost of each of the rollers to insure positive tension thereon.